1. Field of the Invention
The present invention relates to a process for the alkylation of organic aromatic materials in liquid phase which are reacted with olefins in the gaseous phase and the catalyst is in the solid phase. More particularly the invention relates to a countercurrent process.
2. Related Art
Chemical reactions between liquid and gaseous reactants often present difficulties in obtaining intimate contact between phases, especially when the reactions are catalyzed by porous solid catalysts. The three phases, solid, liquid and gas must all be contacted efficiently. In the typical reactor the solid catalyst is retained in a reactor and the reactants passed concurrently over the catalyst, usually downflow. Other common techniques for contacting liquid-gas mixtures with solid catalyst include slurry catalyst, ebulating beds and catalytic or reactive distillation.
Typically the alkylation of aromatic compounds with olefins has been carried out in the liquid phase. See for example U.S. Pat. Nos. 4,469,908; 4,891,458; 5,030,786; 5,081,323 and 5,196,623. More recently the alkylation of organic aromatic compounds with olefins has been carried out in a distillation column reactor. See for example U.S. Pat. Nos. 4,950,834; 5,019,669; 5,113,031; 5,215,725; and 5,243,115. In the distillation column reactor the catalyst is also acting as a distillation structure. The reaction mixture is boiling within the catalyst bed. Generally the olefin is fed as a gas below the catalyst bed and the aromatic compound is fed directly above or into the bed. The heat of reaction causes boil up and lighter materials are taken as overheads and the heavier materials are taken as bottoms. Generally the overheads contains the majority of unreacted aromatic compound and unreacted olefin. The bottoms contains the alkylated product and may also contain small amounts of the unreacted aromatic compound depending upon the efficiency of the stripping section in the distillation column reactor.
Briefly, the present invention is a process for the alkylation of organic aromatic compounds by countercurrent contact of a liquid organic aromatic compound and a gaseous olefin in a reactor containing a fixed bed of solid catalyst. The olefin is fed in the vapor phase below the catalyst bed and the organic aromatic compound is fed in the liquid phase above the catalyst bed.
The countercurrent operation provides a minimum residence time for the alkylation product in contact with the catalyst and thereby a greater selectivity towards the desired product. Because the vapor phase is a major carrier of the olefin a lower olefin concentration in the liquid phase results which provides for a much lower deactivation rate for the catalyst.
The process for the alkylation of organic aromatic compounds comprises the steps of:
(a) feeding a liquid stream containing an organic aromatic compound into a reactor above a bed of solid particulate aromatic alkylation catalyst;
(b) feeding a gaseous stream containing an olefin into the reactor below the bed of solid particulate catalyst;
(c) countercurrently contacting said organic aromatic compound with said olefin and said catalyst to react a portion of said organic aromatic compound with a portion of said olefin to produce an alkylated organic aromatic product under conditions to maintain organic aromatic compound and alkylated organic product in said liquid phase and olefins in said gaseous phase;
(d) withdrawing unreacted gaseous olefin from the reactor at a point above said bed of solid particulate catalyst; and
(e) withdrawing unreacted organic aromatic compound and alkylated organic aromatic product from the reactor at a point below said bed of solid particulate catalyst.